The Home Office minister in charge of the Regulation of Investigatory Powers (RIP) Bill has publicly defended the controversial legislation against accusations that it breeches human rights.

Debate has centred around part three of the Bill - previously in the Electronic Communications Bill - which allows the police to serve written notice to demand either that a communication be decrypted or the private encryption key be handed over.

Critics, including think tank the Foundation for Information Policy Research (FIPR), have argued that the Bill would criminalise the use of computers, turn ISPs into surveillance centres and harm UK ecommerce.

Charles Clarke, Minister of State at the Home Office, said this week that the Bill is in line with the European Human Rights Convention and the development of ecommerce.

"The right to privacy should and must be safeguarded, but the right of law enforcement to be proactive must be protected too," Clarke said at the Scrambling for Safety 2000 Conference in London.

"Law enforcement agencies should be able to understand the contents of material that they lawfully obtain, notwithstanding the fact that it has been protected with some unbreakable new code. But that is the limit of our ambition," he added.

"The new decryption powers require proper authorisation, contain stringent safeguards covering the use and retention of any material obtained under the Bill, and are subject to independent judicial oversight. The Bill does not give the authorities any new powers to obtain material which they cannot already do."

Clarke said the government would pay the extra costs incurred by ISPs as a result of the Bill, but said it "does not expect the costs to be huge". He declined to go into details on this issue.

Oliver Heald, front bench Conservative spokesman on the Bill, said: "The government is legislating without having resolved technical problems. The more effective this interception is, the more expensive it will be."

Concerns that the Bill violates fundamental human rights were raised at the meeting. These include concerns that it would violate the presumption of innocence, would infringe upon the right not to self-incriminate and that there are inadequate safeguards against abuse of the measures.

A legal opinion commissioned by FIPR and human rights organisation Justice said that police powers to unscramble encoded email, contained in the Bill, are likely to breach the European Convention on Human Rights.

Tim Eicke, a barrister at Essex Court Chambers, who wrote the legal opinion, said: "For anyone using encryption, in order to avoid unjustified suspicion and possible wrongful conviction, it would have to be good practice to use stenographic [information hiding] file systems and not to admit to ever having had a key rather than be helpful and co-operative."